The invention is directed to a product for use in the interior of shoes such as insole and middle sole materials which are produced in the form of breadths (continuous sheet form) and then are cut into blanks for use in the shoes, for example in the form of soles. The new material has particularly good foot hygenic properties. Based on its synthesis and the structure, particularly of the polymers, which is present in the new material, it has a greatly improved ability to absorb and give off perspiration which is comparable with that of natural leather.
Natural leather is known for use in insoles and midsoles, particularly for high grade footwear. Because of its good mechanical properties and especially because of its good foot hygenic properties this material is preferred. Under foot hygenic properties there is understood particularly the ability to absorb, in a given case in large amounts, to store and also to give up again perspiration without noticeably changing the mechanical properties of the shoe parts.
It is also known to use insoles and midsoles from leather fiber materials. In this connection, there are used materials of natural and/or synthetic fibers which are impregnated, or bound with suitable synthetic materials as for example, natural or synthetic rubber. Besides partially satisfactory mechanical properties leather fiber materials in comparison to natural leathers exhibit especially the disadvantage of insufficient foot hygenic properties, particularly they do not have sufficient ability to absorb perspiration because of their structure and composition. This ability, however, is a required property particularly for insoles and middle soles.
For synthetic insole and midsole materials, there is the need and thus the starting point for the present invention, to find a material which exhibits good foot hygenic properties and particularly a high ability to absorb perspiration, however, at the same time practically retaining constant or at least retaining sufficient mechanical properties such as tear resistance (tensile strength, stitching resistance, dimensional stability and flexural strength (flexing life).